Method of preforming refractory material prior to rolling.



c ran srarns PATEN MARCELLO VON PIRANI, OF WILMERSDORF, NEAR BERLIN,GERMANY, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEWYORK.

METHOD OF PREFORMING REFRACTORY MATERIAL PRIOR TO ROLLING.

No Drawing.

To all whom it may concern Be it known that I, MAROELLO VON PIRANI, acitizen of the Italian Kingdom, residing at VVilmersdorf, near Berlin,Germany, have invented certain new and useful Improve ments in theMethod of Preforming Refractory Material Prior to Rolling, of which thefollowing is a specification.

In the rolling of refractory metals such as tungsten, which have acertain amount of brittleness, difficulties arise due to the developmentof cracks or fractures. These cracks are caused by the radical changesof form to which the material is subjected, and the greater the changesof form the more cracked the material becomes. The changes of form aregreatest at the beginning of the rolling operation and therefore thedanger of cracking is greatest at this time.

Metals which are in general more or less easy to work show a tendency toa certain degree to crack on being rolled, but these difficulties may bemet by giving to these metals before they come between the rollers, across-section by hammering, forging or the like which nearly correspondsto the crosssection when rolled. Thereby the changes of form in rollingare greatly reduced. Such manipulation, however, cannot be ef fectedwith refractory, brittle metals, since, as is well known, they are notworkable in this sense under ordinary conditions.

The object of this invention is to render these metals work ble and itis accomplished by giving to the material to be rolled a form which issimilar to the cross-section which it is to have after being rolled. Itmight at first be thought that one way of doing this would be by castingit in molds in this cross-sectional form. Practically, however, castingin proper cross-section is not feasible 011 account of theextraordinarily high fusing temperatures of the materials and thedifficulty of making molds Specification of Letters Patent.

Patented Apr. 14L, rare.

Application filed November 23, 1912. Serial No. 733,077.

which can be used for such temperatures. The material would alsounavoidably receive lmpurities in casting. By the method forming myinvention it 1s possible to roll refractory and brittle metals such astungsten, without danger of cracking. According to the invention thematerial, if powdered, is then pressed under heavy pressure into apreliminary shape, and is afterward given a cross-section which issimllar to the cross-section which the article is to have after it hasbeen rolled, and this is done by a manipulation which causes no changesin the interior of the material to be rolled, but is done by purelyexternal working, such as filing, grinding, planing, cutting and thelike. The rolling operation is then begun at about 1000 O. to 1500 G.and the temperature may be gradually lowered during the operation.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. The method of preparing refractory metals for rolling free fromcracks or fractures which consists in giving to the raw metal prior torolling and without changing the structure of its internal portions anexternal shape similar to that of the rolled article and with atransverse section similar to that imposed upon said metal during therolling operation.

2. The step in the method of rolling refractory metal which consists inexternally working the unrolled metal without affecting its internalstructure to a shape having Copies of this patent may be obtained forfive cents each, by addressing the Commissioner of Patents, Washington,D. G.

